Melting and handling cadmium and its alloys



Patented May 12, 1936 PATENT OFFICE MELTING AND HANDLING CADMIUM AND ITS ALLOYS Albert J Phillips,

Highland Park,

Smelting and Refining Company,

Metuchen, and Carl E. Swartz, N. J., assignors to American New York,

N. Y., a corporation of New Jersey No Drawing. Application June 12, 1934, Serial No. 730,253

2 Claims. (01. 75-71) This invention relates to the melting, handling and casting of cadmium and its alloys and more particularly to improvements for inhibiting oxidation of the metal.

When cadmium or alloys of high cadmium content are melted, there is a marked tendency for the cadmium to oxidize. Further, the product resulting from the oxidation is of a flocculent nature which fluffs up and, instead of forming a protective blanket for the remaining metal, allows the oxidation to proceed to such a degree that the metal is often rendered unfit for many commercial uses.

The present invention provides a method for preventing or inhibiting the formation of this detrimental flocculent, powdery cadmium oxide thus yielding improved results in the melting and handling of cadmium and its alloys.

It has been found that by incorporating small amounts of zinc in the cadmium or alloy thereof, the formation of the detrimental reddish brown cadmium oxide can be readily inhibited and in its place a thin, silvery oxide film will form over the metal protecting it from further oxidation. Also the amount of zinc required to effect these desirable results is sufficiently small that the other physical and chemical characteristics of the metal are not materially affected.

Several modes of operation are contemplated by the invention. For example, the beneficial results are readily obtained adding the requisite amount of zinc to the cadmium or cadmium alloys as it is melted. As before stated, only a small amount of zinc is necessary, five hundredths of one per cent having been found to practically eliminate the tendency of the flocculent reddish I 'brown oxide to form in many instances. If the metal is to be held in the liquid state over extended periods of time, small amounts of zinc should be added at intervals to compensate for zinc losses which result by reason of the tendency of the zinc to burn out of the bath.

In melting cadmium and its alloys under salt covers, the tendency of the zinc to leave the metal and thus permit the undesired oxidation when the salt cover is removed appears to be accelerated. However, it has been found that this tendency may be overcome by incorporating in the salt cover an equilibrium amount of a suitable zinc salt such as zinc chloride. In fact, the small amount of zinc necessary to prevent the formation of the undesired flocculent cadmium oxide may be added to the metal by melting the cadmium or cadmium alloy under a fused layer of zinc chloride whereby the reaction ZnCl2+Cd=CdCl2+Zn takes place. In this manner a zinc content up to 0.1% may be imparted to the bath which effectively inhibits the detrimental oxidation which otherwise would ensue upon removal of the salt cover. Further, it is possible to provide the equilibrium amount of zinc necessary to retard or prevent the formation of the reddish brown oxide through the use of a quantity of zinc chloride insuflicient to provide a complete cover for the bath of metal.

It will thus be appreciated that the present invention marks a distinct advance in the art of melting and handling cadmium and its alloys by effectively inhibiting the formation of flocculent cadmium oxide and the detrimental effects which would attend its formation. As previously pointed out, the small amount of zinc necessary to effect the improved results may be added in different manners, for example, by additions of metallic zinc or the use of suitable zinc salts in a fused salt cover. In connection with the latter, it is to be noted that no claim is made to the use of a zinc salt cover for dissolving metallic oxides from the surface of the metal bath or as a cover slag to prevent oxidation by excluding air from the bath surface.

While certain novel features of the invention have been disclosed and are pointed out in-the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The process for maintaining a molten bath of cadmium or cadmium alloy over an extended period of time which consists in imparting to said bath, and maintaining therein, a zinc content not exceeding approximately 0.1% which is sufflcient .to inhibit the formation of detrimental, flocculent cadmium oxide but which is insufficient to impart to the bath a zinc content appreciably in excess of that necessary to inhibit the formation of the undesired ,oxide.

2. The process for inhibiting oxidation of a molten bath of cadmium or alloy thereof which comprises imparting to the molten bath a zinc content of approximately 0.05% to approximately 0.1% and adding further quantities of zinc to said bath at intervals to maintain the zinc content within that range.

' ALBERT J. PHILLIPS.

CARL E. SWARTZ. 

